Laminated substrate using fiber-reinforced thermoplastic plastic, and molded product manufacturing method using same

ABSTRACT

Provided is a laminated substrate wherein a sheet-shaped material with a porosity of 50-99% is laminated onto at least one surface of a prepreg substrate which includes a reinforcing fiber and a thermoplastic resin.

TECHNICAL FIELD

The present invention relates to a laminated substrate characterized byhaving excellent shapeability into a complicated shape at the time ofstamping molding and being moldable particularly at a low moldtemperature, and a method for manufacturing a molded product using thislaminated substrate. More particularly, the invention relates to alaminated substrate which easily conforms to the molding of athree-dimensional shape such as a rib or a boss, and retains mechanicalstrength as a structural member, and which is an intermediate substratemade of a fiber-reinforced thermoplastic plastic that is suitably usedfor, for example, aircraft members, automobile members, and sportsgoods; and to a method for manufacturing the laminated substrate.

The present application claims priority on Japanese Patent No.2013-252980 filed in Japan on Dec. 6, 2013, the disclosure of which isincorporated herein by reference.

BACKGROUND ART

Regarding a method for molding a fiber-reinforced thermoplastic plastic,stamping molding by which a substrate obtained by impregnatingreinforcing fibers with a thermoplastic resin (prepreg substrate) isshaped into an intended shape by heating and pressing with a press orthe like, is most generally carried out. A fiber-reinforced plasticmolded product obtained thereby can be designed to have neededmechanical properties by setting the length and content of thereinforcing fiber to appropriate length and content. However, in a casein which the mold temperature is low, there is a problem that sufficientstamping moldability is not obtained, and shaping into a complicatedshape such as a rib or a boss is insufficiently achieved. On thecontrary, in a case in which the mold temperature is high, sufficientstamping moldability is obtained; however, there is a problem thatsolidification or crystallization within the mold occurs insufficiently,and significant deformation occurs after the molded product is taken outof the mold.

In order to solve this problem, there has been suggested a heating andcooling system of performing molding by heating the mold at a hightemperature, subsequently cooling the mold, and taking out the moldedproduct (Patent Documents 1 to 3). However, these systems requireenormous equipment costs, and there is also a problem that there arerestrictions on the mold shape.

Generally, in order to enhance the fluidity of fiber-reinforcedthermoplastic plastics, it is considered effective to reduce the contentof the reinforcing fibers, or to shorten the length of the reinforcingfibers. However, in this method, it is known that mechanical propertiesare also deteriorated, and it is difficult to obtain molded productshaving intended strength.

Furthermore, it is generally known that in order to enhance the fluidityof fiber-reinforced plastics, it is effective to decrease the viscosityof the matrix resin. However, it is known that the mechanical propertiesare deteriorated even in this method, and it is difficult to obtainmolded products having intended strength.

Furthermore, it can be expected to enhance fluidity at low temperatureby lowering the melting point or glass transition point of the matrixresin of a fiber-reinforced plastic. However, in this method, there is aproblem that the mechanical properties at high temperature of a moldedproduct are deteriorated.

CITATION LIST Patent Document

-   Patent Document 1: JP 3977565 B1-   Patent Document 2: JP 4121833 B1-   Patent Document 3: JP 4242644 B1

SUMMARY OF THE INVENTION Problem to be Solved by the Invention

The invention is intended to solve the problems associated with theprior art as described above, and it is an object of the invention toprovide a laminated substrate which has excellent shapeability into acomplicated shape at the time of stamping molding and can be molded at aparticularly low mold temperature, and a method for manufacturing thelaminated substrate.

Means for Solving Problem

The inventors of the invention conducted a thorough investigation, andas a result, the inventors found that the problems described above canbe solved by the means described below, thus completing the invention.That is, the invention solves the problems described above by means of alaminated substrate in which a sheet-like material having a porosity offrom 50% to 99% is laminated on at least one surface of a prepregsubstrate that includes reinforcing fibers and a thermoplastic resin.

The gist of the invention lies in the following items [1] to [12].

[1] A laminated substrate, having a sheet-like material having aporosity of from 50% to 99% laminated on at least one surface of aprepreg substrate that includes reinforcing fibers and a thermoplasticresin.

[2] The laminated substrate according to the item [1], wherein theprepreg substrate is a prepreg laminated substrate in which pluralsheets of prepregs each including the reinforcing fibers that areunidirectionally oriented and the thermoplastic resin, are laminated.

[3] The laminated substrate according to the item [1], wherein theprepreg substrate is a prepreg substrate in which fiber bundles of thereinforcing fibers or single fibers of the reinforcing fibers aredispersed in the thermoplastic resin.

[4] The laminated substrate according to the item [1], wherein theprepreg substrate is a prepreg substrate in which rectangular chips of aprepreg including the reinforcing fibers that are unidirectionallyoriented, are dispersed in a random fashion.

[5] The laminated substrate according to any one of the items [1] to[4], wherein the length of the reinforcing fibers that constitute theprepreg substrate is 10 mm to 100 mm.

[6] The laminated substrate according to any one of the items [1] to[5], wherein the sheet-like material is a sheet formed from athermoplastic resin.

[7] The laminated substrate according to any one of the items [1] to[5], wherein the sheet-like material is a sheet formed from inorganicfibers.

[8] The laminated substrate according to any one of the items [1] to[7], wherein the sheet-like material is a nonwoven fabric.

[9] The laminated substrate according to any one of the items [1] to[6], wherein the sheet-like material is a foamed sheet.

[10] The laminated substrate according to any one of the items [1] to[9], wherein the thickness of the sheet-like material is from 0.01 mm to10 mm.

[11] The laminated substrate according to any one of the items [1] to[10], wherein at least one surface of the prepreg laminated substrate iscovered by the sheet-like material at a proportion of 30% by area ormore relative to the total area of the at least one surface of theprepreg laminated substrate.

[12] The laminated substrate according to any one of the items [1] to[11], wherein the prepreg substrate and the sheet-like material are notadhered.

[13] The laminated substrate according to any one of the items [1] to[12], wherein the laminated substrate is a laminated substrate forstamping molding.

[14] A method for manufacturing a molded product of a laminatedsubstrate, the method including (1) heating a prepreg substrateincluding reinforcing fibers and a thermoplastic resin, to a temperaturehigher than or equal to the melting point or the glass transition pointof the thermoplastic resin that constitutes the prepreg, and thenlaminating a sheet-like material having a porosity of from 50% to 99% onat least one surface of the prepreg substrate, to thereby obtain alaminated substrate; or (2) laminating a sheet-like material having aporosity of from 50% to 99% on a prepreg substrate including reinforcingfibers and a thermoplastic resin on at least one surface of the prepregsubstrate, and then heating the laminate thus obtained to a temperaturehigher than or equal to the melting point or the glass transition pointof the thermoplastic resin that constitutes the prepreg, to therebyobtain a laminated substrate,

the method subsequently including introducing the laminated substrateinto a mold set to a temperature lower than or equal to the meltingpoint or the glass transition point of the thermoplastic resin thatconstitutes the prepreg, and then stamping molding the laminatedsubstrate. [15] The manufacturing method according to the item [14],wherein the temperature of the mold is 50° C. to 200° C.

Effect of the Invention

According to the invention, a laminated substrate which has excellentshapeability into a complicated shape and can be molded particularly ata low mold temperature, and a method for manufacturing a molded productusing this laminated substrate, can be obtained.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram illustrating a laminated substrate having asheet-like material having a porosity of from 50% to 99% laminated onboth surfaces of a prepreg substrate of the invention.

FIG. 2 is a diagram illustrating a molded product used in Examples ofthe invention.

FIG. 3 is a diagram illustrating an example of the prepreg used in theinvention.

MODE(S) FOR CARRYING OUT THE INVENTION

A first exemplary embodiment of the invention relates to a laminatedsubstrate in which a sheet-like material having a porosity of from 50%to 99% is laminated on at least one surface of a prepreg laminatedsubstrate that includes reinforcing fibers and a thermoplastic resin.

Generally, in stamping molding of a prepreg substrate, an intendedmolded product is obtained by heating a prepreg substrate to atemperature higher than or equal to the melting point or the glasstransition point of the thermoplastic resin using a heating facilitysuch as an IR heater, subsequently inserting the prepreg substrate intoa mold that is set to a temperature lower than or equal to the meltingpoint or the glass transition point of the thermoplastic resin, andpressing the prepreg substrate under pressure. At that time, since theviscosity of the thermoplastic resin increases as a result of coolingthrough the mold surface, noticeable deterioration of stampingmoldability occurs.

In order to prevent this cooling through the mold surface, it ispreferable to provide a heat-insulating layer on the surface of theprepreg substrate that is brought into contact with the mold, and tomaintain the temperature of the prepreg substrate at a high temperature.Also, it is preferable that this heat-insulating layer rapidly passeson, after shaping, the cooling through the mold to the prepregsubstrate, so that solidification or crystallization proceedssufficiently.

It is preferable that this heat-insulating layer is in a sheet form soas to cover a portion or the entirety of the prepreg substrate, islightweight, and includes air since a sufficient heat-insulating effectis desired. According to the invention, from the viewpoint of havinghigh heat insulation properties, it is preferable that at least onesurface of a prepreg laminated substrate is covered by a sheet-likematerial having a porosity of from 50% to 99% at a proportion of 30% byarea or more, more preferably 50% by area or more, relative to the totalarea of the at least one surface of the prepreg laminated substrate.More specifically, the coverage is 30% to 100% by area, and morepreferably 50% to 100% by area.

(Sheet-Like Material Having Porosity of from 50% to 99%)

The porosity of the sheet-like material that is used as aheat-insulating layer is preferably from 50% to 99%, in order to retainsufficient heat insulation properties. Even more preferably, theporosity is preferably from 60% to 99%. Furthermore, the thickness ofthis sheet-like material is not particularly limited; however, it ismore desirable if the sheet-like material is thinner, as long as theheat insulation properties can be maintained. The thickness ispreferably from 0.01 mm to 10 mm, and more preferably from 0.05 mm to 5mm. Meanwhile, the thickness of the sheet-like material can be measuredby measuring the thickness of the sheet-like material at plural sitesusing vernier calipers or a micrometer, and determining the averagevalue of the numbers.

Here, the porosity is a cumulative fraction occupied by the air phase inthe total volume of the sheet-like material, and the porosity can bemeasured by the procedure: porosity (%)={1−(total volume of materialconstituting sheet-like material/total volume of sheet-likematerial)}×100.

It is preferable that this sheet-like material retains pores beforestamping molding, and after stamping molding, the pores are lost. Inorder to do so, the sheet-like material is preferably a nonwoven fabricor a foamed sheet.

Furthermore, it is preferable that the prepreg substrate and thesheet-like material are not adhered before stamping molding. Here,“adhesion” means integration of the prepreg substrate and the sheet-likematerial by means of an adhesive or thermal fusion. Since the prepregsubstrate and the sheet-like material are not adhered before stampingmolding, heat insulation properties can be maintained, and since theprepreg and the sheet-like material are adhered after stamping molding,mechanical strength can be enhanced. Meanwhile, the porosity of thesheet-like material that has been stamping molded is preferably 0% to2%, and more preferably 0% to 1%.

Regarding the fiber used for the nonwoven fabric, the kind of the fiberis not particularly limited, and inorganic fibers, resin fibers, plantfibers, metal fibers, or fibers of hybrid constitutions combining thosefibers can be used. Examples of the inorganic fibers include carbonfibers, graphite fibers, silicon carbide fibers, alumina fibers,tungsten carbide fibers, boron fibers, and glass fibers. Examples of theresin fibers include aramid fibers, high-density polyethylene fibers,other general polypropylene fibers, nylon fibers, and polyesters.Examples of the plant fibers include cellulose fibers of hemp, jute,bamboo, and the like. Examples of the metal fibers include fibers ofstainless steel, iron, and the like, and carbon fibers coated withmetals may also be used. Among them, carbon fibers, glass fibers,polypropylene fibers, nylon fibers, and polyester fibers are preferred.

Regarding the resin used for the foamed sheet, the kind of the resin isnot particularly limited as long as the resin is a thermoplastic resin,and a polyamide (nylon 6, nylon 66, or the like), a polyolefin(polyethylene, polypropylene, or the like), a modified polyolefin, apolyester (polyethylene terephthalate, polybutylene terephthalate, orthe like), a polycarbonate, a polyamideimide, polyphenylene oxide, apolysulfone, a polyethersulfone, polyether ether ketone, polyetherimide,polystyrene, ABS, polyphenylene sulfide, a liquid crystal polyester, acopolymer of acrylonitrile and styrene, or the like can be used.Furthermore, mixtures of these polymers may also be used. Furthermore, acopolymerization product such as copolymerized nylon of nylon 6 andnylon 66 may also be used. Among them, a polyamide and a polyolefin arepreferred. Also, if necessary, a flame retardant, a weather resistanceimproving agent, another oxidation inhibitor, a thermal stabilizer, anultraviolet absorber, a plasticizer, a lubricating agent, a colorant, acompatibilizer, a conductive filler, and the like may be added to theresin.

(Prepreg Substrate Including Reinforcing Fibers and Thermoplastic Resin)

The prepreg substrate including reinforcing fibers and a thermoplasticresin used for the invention may be in any form, and examples thereofinclude a laminate of prepregs, a random dispersion of chopped prepregs,and a dispersion of fiber bundles of the aforementioned reinforcingfibers (hereinafter, also called fiber bundles or reinforcing fiberbundles) or single fibers of the aforementioned reinforcing fibers(hereinafter, also called single fibers) in a thermoplastic resin. Thesemay be used in an intact state, or may be used after being fixed into asheet shape by hot pressing.

The prepreg substrate produced by laminating prepregs may be a substratein which prepregs having the reinforcing fibers unidirectionallyoriented are unidirectionally laminated, a substrate in which prepregsare quasi-isotropically oriented, or a substrate in which prepregs areperpendicularly laminated; however, there is no particular reason tostick to a certain lamination method. Furthermore, the prepreg may havean incision having a depth that cuts the reinforcing fibers in adirection that traverses the length direction of the reinforcing fibers.In FIG. 3, straight line-shaped incisions are provided obliquely to theorientation direction of the reinforcing fibers; however, the incisionsmay also be provided perpendicularly. The shape of the incisions may bea linear shape, or may be a curved line shape. As the average fiberlength of the reinforcing fibers produced at the time of incision isshorter, superior stamping moldability is obtained, and as the averagefiber length is longer, superior mechanical properties are obtained.However, generally, the average fiber length is preferably from 10 mm to100 mm in view of the balance between the two. Meanwhile, the averagefiber length can be determined by measuring all of the cutting lengths(10 in FIG. 3) on a prepreg, and calculating the average value of thenumbers. It is preferable that the incisions are formed such that theaverage fiber length is within the value range described above.Meanwhile, as illustrated in FIG. 3, the length 10 of a cut reinforcingfiber means the length from an incision to another incision. The sumtotal of the lengths 9 of incisions (hereinafter, also called cuttinglength) in 1 m² of a prepreg is preferably 20 m to 200 m, and morepreferably 30 m to 150 m. The angle 8 formed by an incision 6 and areinforcing fiber 7 is preferably 30° to 90°. Meanwhile, the angle 8 ina case in which the shape of the incisions is a curved line when viewedin a planar view can be measured, as the angle formed by a reinforcingfiber and an incision, in the same manner as in the case of a linearincision. In a case in which the prepreg substrate has incisions, it ispreferable that the incisions cut the reinforcing fibers from the upperface to the lower face of the prepreg substrate. Furthermore, athermoplastic resin layer may be included in all or some of the spacesbetween laminated prepregs. As the fiber volume percentage content (Vf)of the reinforcing fibers in the prepreg is smaller, superior stampingmoldability is obtained, and as the fiber volume percentage content islarger, superior mechanical properties are obtained. However, generally,the fiber volume percentage content is preferably from 20% to 60%relative to the total volume of the prepregs, in view of the balancebetween the two. For the value of Vf as such, a value determined usingthe following formula, from the density ρc of the prepreg obtained by,for example, a water displacement method; the density ρf of the fibersobtained by a similar method; the mass W of the prepreg; and the weightW1 obtained after the prepreg is combusted and the resin is lost, isused.

Wf=(W−W1)×100/W  Formula (3)

Vf=Wf×ρc/ρf  Formula (4)

In connection with rectangular prepreg chips, the random dispersion ofchopped prepregs is preferably a product in which a prepreg in whichreinforcing fibers are unidirectionally oriented is cut intorectangular-shaped pieces (chopped prepregs), and the prepreg pieces aredispersed in a random fashion. There are no particular limitations onthe size of the rectangle produced at the time of cutting; however, itis preferable to cut the prepreg so as to obtain an average fiber lengthof from 10 mm to 100 mm, because excellent stamping moldability andmechanical properties are obtained. Furthermore, in order to dispersechopped prepregs in a random fashion, a smaller rectangular shape ispreferred, and the length of one edge is preferably from 5 mm to 50 mm.As the fiber volume percentage content (Vf) of the reinforcing fibers inthe prepreg is smaller, superior stamping moldability is obtained, andas the fiber volume percentage content is larger, superior mechanicalproperties are obtained. However, generally, the fiber volume percentagecontent is preferably from 20% to 60% relative to the total volume ofthe prepreg in view of the balance of the two.

In the dispersion of fiber bundles of reinforcing fibers or singlefibers of reinforcing fibers in a thermoplastic resin, the fiber lengthis not particularly limited; however, from the viewpoint of achieving abalance between this fluidity and mechanical properties, the averagefiber length of the reinforcing fibers is preferably from 1 mm to 20 mm.According to another embodiment, the average fiber length is preferably10 mm to 100 mm. As the fiber volume percentage content (Vf) of thereinforcing fibers in the prepreg is smaller, superior stampingmoldability is obtained, and as the fiber volume percentage content islarger, superior mechanical properties are obtained. However, generally,the fiber volume percentage content is preferably from 10% to 30%relative to the total volume of the prepreg, in view of the balancebetween the two.

Regarding the reinforcing fibers used for the prepreg substrate of theinvention, the kind of the reinforcing fibers is not particularlylimited, and inorganic fibers, resin fibers, plant fibers, metal fibers,or fibers having a hybrid constitution combining those fibers can beused. Examples of the inorganic fibers include carbon fibers, graphitefibers, silicon carbide fibers, alumina fibers, tungsten carbide fibers,boron fibers, and glass fibers. Examples of the resin fibers includearamid fibers, high-density polyethylene fibers, other general nylonfibers, and polyesters. Examples of the plant fibers include cellulosefibers of hemp, jute, bamboo, and the like. Examples of the metal fibersinclude fibers of stainless steel, iron, and the like, and carbon fiberscoated with metals may also be used. Among these, in consideration ofthe mechanical characteristics such as strength of the final moldedproduct, carbon fibers are preferable. Furthermore, average fiberdiameter of the reinforcing fibers is preferably 1 μm to 50 μm, and morepreferably 5 μm to 20 μm. Here, the diameter means the diameter of across-section produced when a reinforcing fiber is cut in a directionperpendicular to the length direction. The average fiber diameter can bemeasured by measuring plural fibers with a micrometer, and determiningthe average value of the numbers.

Regarding the resin used for the prepreg substrate of the invention, thekind of the resin is not particularly limited as long as the resin is athermoplastic resin, and a polyamide (nylon 6, nylon 66, or the like), apolyolefin (polyethylene, polypropylene, or the like), a modifiedpolyolefin, a polyester (polyethylene terephthalate, polybutyleneterephthalate, or the like), a polycarbonate, a polyamideimide,polyphenylene oxide, a polysulfone, a polyethersulfone, polyether etherketone, polyetherimide, polystyrene, ABS, polyphenylene sulfide, aliquid crystal polyester, a copolymer of acrylonitrile and styrene, orthe like can be used. Furthermore, mixtures of these polymers may alsobe used. Among them, a polyamide and a polyolefin are preferred.Furthermore, a copolymerization product such as copolymerized nylon ofnylon 6 and nylon 66 may also be used. Also, if necessary, a flameretardant, a weather resistance improving agent, another oxidationinhibitor, a thermal stabilizer, an ultraviolet absorber, a plasticizer,a lubricating agent, a colorant, a compatibilizer, a conductive filler,and the like may be added to the resin.

In regard to the prepreg substrate including reinforcing fibers and athermoplastic resin, it is preferable that the reinforcing fibers arecarbon fibers, and the thermoplastic resin is a modified polypropyleneor a polyamide resin. The sheet-like material is preferably at least oneselected from the group consisting of a polyester nonwoven fabric, aglass nonwoven fabric, and a foamed polyamide, and the porosity ispreferably 90% to 95%.

In the following description, an embodiment of the method formanufacturing a molded product using a laminated substrate according toa second exemplary embodiment of the invention will be explained;however, the invention is not intended to be particularly limitedthereby.

The second exemplary embodiment of the invention relates to a method formanufacturing a molded product of a prepreg laminated substrate, themethod including: (1) heating a prepreg substrate including reinforcingfibers and a thermoplastic resin to a temperature higher than or equalto the melting point or the glass transition point of the thermoplasticresin that constitutes the prepreg, and then laminating a sheet-likematerial having a porosity of from 50% to 99% on at least one surface ofthe prepreg substrate, to thereby obtain a laminated substrate; or (2)laminating a sheet-like material having a porosity of from 50% to 99% ona prepreg substrate including reinforcing fibers and a thermoplasticresin on at least one surface of the prepreg substrate, and then heatingthe laminate thus obtained to a temperature higher than or equal to themelting point or the glass transition point of the thermoplastic resinthat constitutes the prepreg, to thereby obtaining a laminatedsubstrate, and the method subsequently including introducing thelaminated substrate into a mold that is set to a temperature lower thanor equal to the melting point or the glass transition point of thethermoplastic resin that constitutes the prepreg, and then stampingmolding the laminated substrate.

The laminated substrate according to the first exemplary embodiment ofthe invention can be produced by a method for manufacturing a laminatedsubstrate, the method including (1) heating a prepreg substrateincluding reinforcing fibers and a thermoplastic resin to a temperaturehigher than or equal to the melting point or the glass transition pointof the thermoplastic resin that constitutes the prepreg, and thenlaminating a sheet-like material having a porosity of from 50% to 99% onat least one surface of the prepreg substrate, or (2) laminating asheet-like material having a porosity of from 50% to 99% on a prepregsubstrate including reinforcing fibers and a thermoplastic resin on atleast one surface of the prepreg substrate, and then heating thelaminate thus obtained to a temperature higher than or equal to themelting point or the glass transition point of the thermoplastic resinthat constitutes the prepreg.

The temperature of the mold is preferably 50° C. to 200° C., and morepreferably 100° C. to 180° C.

Stamping molding is to integrate the sheet-like material by heating andpressing. The pressure at the time of stamping molding is preferably 0.1MPa to 10 MPa.

(Prepreg)

The prepreg used for the prepreg substrate of the invention can beobtained by, for example, preparing two sheets of a thermoplastic resinproduced in a film form, inserting a reinforcing fiber sheet produced byarranging reinforcing fibers in a sheet form between the two sheets ofthe thermoplastic resin, and performing heating and pressing. Morespecifically, two sheets of a film formed from a thermoplastic resin aresent out from two rolls, a reinforcing fiber sheet supplied at the sametime from a roll of the reinforcing fiber sheet is inserted between thetwo sheets of film, and then the assembly is heated and pressurized.Regarding the means for heating and pressurizing, any known means can beused, and two or more heat rolls may be utilized, or a means requiring amultistage process of using plural pairs of a preheating apparatus and aheat roll, or the like may also be employed. Here, the thermoplasticresin that constitutes the film is not necessarily of one kind, or afilm formed from another kind of thermoplastic resin may be furtherlaminated thereon using an apparatus such as described above.

The heating temperature may vary depending on the kind of thethermoplastic resin; however, usually, the heating temperature ispreferably 100° C. to 400° C., and more preferably 150° C. to 350° C. Onthe other hand, the pressure at the time of pressurization is usuallypreferably 0.1 MPa to 10 MPa. When the pressure is in this range, it ispreferable because a prepreg can be impregnated with a thermoplasticresin between the reinforcing fibers included in the prepreg.Furthermore, for the prepreg that can be used for the laminatedsubstrate of the invention, a commercially available prepreg can also beused.

(Prepreg Laminated Substrate)

A prepreg laminated substrate is produced by laminating prepregsobtained as described above so as to attain unidirectional lamination,quasi-isotropic lamination, or perpendicular lamination, and regardingthe prepreg laminated substrate of the invention, it is preferable tolaminate 4 to 96 layers of prepregs. Furthermore, the prepreg may haveincisions so as to cut the continuous fibers, by utilizing a lasermarker, a cutting plotter, a punching die or the like.

(Random Prepreg Substrate)

The prepreg obtained as described above is processed into a tape shapehaving a narrow width using a slitter or the like, and then the prepregis chopped into a certain length using a pelletizer, a guillotinecutter, a roller cutter or the like to obtain chopped prepregs.Regarding the method of dispersing chopped prepregs so as to obtain arandom fiber direction, for example, a method of freely dropping choppedprepregs from a high position, and depositing the chopped prepregs on acontainer or the die of a mold, which passes over a belt conveyor; amethod of generating an air stream by blowing air into the fallingroute; a method of providing baffle plates in the falling route; or amethod of stirring deposited chopped prepregs and then disposing thechopped prepregs on a die, can be appropriately employed. In regard tothe laminate described above, it is preferable that the number oflaminations of the chopped prepregs is 2 to 100 layers.

(Fiber Bundle or Single Fiber-Dispersed Prepreg Substrate)

Regarding the method of satisfactorily dispersing fiber bundles ofreinforcing fibers or single fibers of reinforcing fibers in a matrixresin, for example, the following method may be used. A method ofcutting reinforcing fibers to a certain length using a guillotinecutter, a roller cutter or the like, also cutting a matrix resin, afterspinning, into a fibrous form having a certain length, subsequentlydispersing the two materials using a stirrer in a large amount of water,subsequently extracting water through a filter, and thereby uniformlydispersing the reinforcing fiber bundles in the matrix resin, can beemployed. In the method described above, it is preferable that theweight concentration of the reinforcing fibers and the matrix resin inwater is 1% or less relative to the total weight of the uniformlydispersed dispersion liquid (including water, the reinforcing fibers,and the matrix resin). Furthermore, at that time, the dispersion liquidmay include an adhesive for bonding the reinforcing fiber bundles andthe fibrous resin in water.

(Nonwoven Fabric)

In a case in which a nonwoven fabric is used as a heat-insulating layeron a portion or the entirety of the prepreg substrate surface obtainedby the method described above, in order to produce the nonwoven fabricdescribed above, for example, the following method may be used. A methodof dispersing a fibrous material having an average fiber length of 5 mmto 100 mm in a random state by a carding method or an air-laid method toobtain a sheet form, and then bonding the fibers using spraying of anadhesive, thermal fusion, needle punching or the like, can be employed.

Furthermore, the nonwoven fabric that can be used for the laminatedsubstrate of the invention, a commercially available nonwoven fabric canalso be used.

(Foamed Sheet)

In a case in which a foamed sheet is used as a heat-insulating layer ona portion or the entirety of the prepreg substrate surface obtained bythe method described above, in order to produce the foamed sheet, forexample, the following method may be used. A method of obtaining afoamed sheet having an intended porosity by mixing thermoplastic resinpellets and a foaming agent, introducing the mixture into a sheetmolding machine, and cooling the resin sheet foaming through a die exitusing plural cooling rolls, can be employed.

Furthermore, regarding the foamed sheet that can be used for thelaminated substrate of the invention, a commercially available foamedsheet can also be used.

(Method for Manufacturing Laminated Substrate)

The molded product of a laminated substrate according to the firstexemplary embodiment of the invention can be produced by a manufacturingmethod, which includes (1) heating a prepreg substrate includingreinforcing fibers and a thermoplastic resin to a temperature higherthan or equal to the melting point or the glass transition point of thethermoplastic resin that constitutes the prepreg, and then laminating asheet-like material having a porosity of from 50% to 99% on at least onesurface of the prepreg substrate to thereby obtain a laminatedsubstrate; or (2) laminating a sheet-like material having a porosity offrom 50% to 99% on a prepreg substrate including reinforcing fibers anda thermoplastic resin on at least one surface of the prepreg substrate,and then heating the laminate thus obtained to a temperature higher thanor equal to the melting point or the glass transition point of thethermoplastic resin that constitutes the prepreg to thereby obtain alaminated substrate, the method subsequently including introducing thelaminated substrate into a mold that is set to a temperature higher thanor equal to the melting point or the glass transition point of thethermoplastic resin that constitutes the prepreg, and then stampingmolding the laminated substrate.

The heating temperature may vary depending on the kind of thethermoplastic resin; however, usually, the heating temperature ispreferably a temperature higher by 10° C. to 100° C. than the meltingpoint or the glass transition point. Furthermore, in a case in which thesoftening point of the sheet-like material is lower than the heatingtemperature, it is preferable to adopt the method described in item (1);and in a case in which the softening point of the sheet-like material ishigher than the heating temperature, it is preferable to adopt themethod of item (2). The mold temperature may vary depending on the kindof the thermoplastic resin; however, usually, the mold temperature ispreferably a temperature lower by 0° C. to 200° C. than the meltingpoint or the glass transition point. Furthermore, if the pressure at thetime of stamping molding is high, as the pressure is higher, moresatisfactory stamping moldability is obtained. Therefore, the pressureapplied to the molded product is usually preferably 0.1 MPa to 50 MPa.

The laminated substrate according to the first exemplary embodiment ofthe invention is preferably a laminated substrate for stamping molding.That is, the laminated substrate according to the first exemplaryembodiment of the invention is preferably used as a material formanufacturing a molded product by stamping molding. The method for usingthe laminated substrate according to the first exemplary embodiment ofthe invention as a laminated substrate for stamping molding includes astep of inserting a laminated substrate into a mold and then applyingpressure thereto; a step of cooling the laminated substrate bymaintaining the laminated substrate therein for a certain period oftime; and a step of taking out the laminated substrate.

The pressing force at the time of applying pressure is preferably 5 t to500 t.

The time for applying pressure is preferably 10 seconds to 1800 seconds.

EXAMPLES

Hereinafter, the invention will be more specifically explained by way ofExamples; however, the invention is not intended to be limited to theinventions described in Examples.

(Evaluation of Moldability)

Since the laminated substrate of the invention has satisfactory fluidityat the time of molding, the laminated substrate can be molded intovarious complicated shapes. Such fluidity can be evaluated such that,for example, when a laminated substrate is heated and then is pressedinside a mold having a complicated shape such as a rib, fluidity can beevaluated based on whether the laminated substrate has filled up to thetip of the rib. Specifically, a laminated substrate having a thicknessof about 2 mm is cut out into a size of 380 mm×45 mm, and is maintainedfor a certain time inside an IR heater (manufactured by NGK Kiln TechCorp.; product name: far-infrared heater type heating furnace). Thelaminated substrate is maintained for 60 seconds in a rib-attached hatchannel die installed in a 300-t press (manufactured by KawasakiHydromechanics Corp.; product name: TMP2-300) at a pressing force of 75t, and a molded product as illustrated in FIG. 2 was obtained. As aresult, the case in which the laminated substrate had completely filledup to the tip of the rib was evaluated as ◯, and the case in which therib was not completely filled was evaluated as X.

Example 1

Carbon fibers (manufactured by Mitsubishi Rayon Co., Ltd., product name:PYROFILL (registered trademark) TR-50S15L) were aligned into a planarform such that the directions of the reinforcing fibers would be asingle direction, and thereby a reinforcing fiber sheet having a areaweight of 72.0 g/m² was obtained. The two surfaces of this reinforcingfiber sheet were interposed between films made of an modifiedpolypropylene resin (manufactured by Mitsubishi Chemical Corp., productname: MODIC (registered trademark) P958, area weight: 36.4 g/m²), thereinforcing fiber sheet was impregnated with the thermoplastic resinusing calendar rolls. Thus, a prepreg having a fiber volume percentagecontent (Vf) of 33% and a thickness of 0.12 mm was obtained.

The prepreg thus obtained was cut out into a square which measured 300mm on each side, and incisions were inserted at a constant interval asillustrated in FIG. 3 using a cutting plotter (manufactured by LaserckCorp., product name: L-2500). At that time, incision processing wasperformed, in which areas extending to the interior by 5 mm from theedges of the sheet were excluded, the reinforcing fibers had a constantlength L of 25.0 mm and an average cutting length l of 42.4 mm, and theangle θ formed by a slit that cuts the fibers and a reinforcing fiberwhen viewed in a planar view was 45°.

Sixteen layers of prepregs having incisions inserted therein, which wereobtained as described above, were superposed quasi-isotropically([0/45/90/−45]s2), and the prepregs were spot-welded with an ultrasonicwelding machine (manufactured by Emerson Japan, Ltd., product name:2000LPt) to thereby produce a prepreg substrate.

The prepreg substrate obtained as such was disposed inside a mold cavitywhich measured 300 mm on each of four edges and had a depth of 1.5 mm,and the mold was maintained, using a compression molding machine(manufactured by Shinto Metal Industries Corp., product name:SFA-50HH0), for 7 minutes under the conditions of 220° C. and an oilpressure indication of 0 MPa with a high temperature side press.Subsequently, the mold was maintained for 7 minutes under the conditionsof an oil pressure indication of 2 MPa (pressing pressure: 0.55 MPa) atthe same temperature, and then the mold was transferred to a coolingpress and maintained for 3 minutes at 30° C. and an oil pressureindication of 5 MPa (pressing pressure: 1.38 MPa). Thereby, anintegrated prepreg substrate was obtained.

The prepreg substrate obtained as such was cut into four sheets eachhaving a size of 380 mm×45 mm, and two sets of two sheets superposedtogether were heated for 5 minutes with an IR heater at 280° C.Thereafter, two sets of the heated prepreg substrates were superposed,and the resultant was disposed at the center of a polyester nonwovenfabric (manufactured by Takayasu Co., Ltd.; ARAFUNON NEEPUN C-100-107;porosity: 90%) having a size of 360 mm×100 mm at normal temperature suchthat the nonwoven fabric came under the prepreg substrates. Thus, alaminated substrate was produced. Immediately thereafter, the laminatedsubstrate was inserted into a rib-attached hat channel mold that wasinstalled in a 300-t press and heated to 90° C. such that the nonwovenfabric was brought into contact with the upper surface of a lower mold,and the laminated substrate was pressured for 60 seconds at a pressingforce of 75 t. Thus, a molded product was obtained.

The molded product obtained as such had a top panel 4, a rib part 3, andflange parts 4 as illustrated in FIG. 2. The molded product thusobtained had satisfactory surface gloss, and was filled with thelaminated substrate up to the tips of the flange parts 5 and the ribpart 3.

Example 2

The prepreg substrate obtained in the same manner as in Example 1 wascut out into four sheets each having a size of 380 mm×45 mm, and twosheets thereof were superposed to provide two sets. One set thereof wasdisposed at the center of a glass fiber nonwoven fabric (manufactured byOribest Co., Ltd.; GRABESTOS FBP-025; porosity: 95%) cut out into a sizeof 380 mm×90 mm such that the nonwoven fabric came under the prepregsubstrate. Thus, a laminated substrate was produced. Those were heatedfor 5 minutes with an IR heater at 280° C., and then one set without thenonwoven fabric was disposed on the nonwoven fabric-attached set, andimmediately thereafter, the assembly was inserted into a rib-attachedhat channel mold that was installed in a 300-t press and heated to 80°C. such that the nonwoven fabric was brought into contact with the uppersurface of a lower mold, and the laminated substrate was pressured for60 seconds at a pressing force of 75 t.

The molded product obtained as such had satisfactory surface gloss, andwas filled with the laminated substrate up to the tip of the rib.

Comparative Example 1

A laminated substrate was produced in the same manner as in Example 1,except that the prepreg substrate was heated and pressed in the samemanner as in Example 1, but a polyester nonwoven fabric was not used.Thus, a molded product was obtained. The molded product obtained as suchhad satisfactory surface gloss, but a portion of the rib tip was notfilled with the laminated substrate.

Comparative Example 2

A laminated substrate was produced in the same manner as in Example 1,except that the laminated substrate was heated and pressed in the samemanner as in Example 1, but a low-foamed polypropylene sheet(manufactured by Mitsui Chemical Tohcello, Inc.; HOPPOTO; porosity: 30%)was used instead of the polyester nonwoven fabric. Thus, a moldedproduct was obtained.

The molded product obtained as such had satisfactory surface gloss;however, a portion of the rib tip was not filled with the laminatedsubstrate.

Comparative Example 3

A laminated substrate was produced in the same manner as in ComparativeExample 1, without using a polyester nonwoven fabric, and the laminatedsubstrate was heated with an IR heater and was subjected to stampingmolding at a mold temperature of 130° C.

The molded product obtained as such had no surface gloss, gas retentionoccurred at the rib tip, and the filling was insufficiently achieved.

Example 3

Carbon fibers (manufactured by Mitsubishi Rayon Co., Ltd., product name:PYROFILL (registered trademark) TR-50S15L) were aligned unidirectionallyin a planar form, and thereby a reinforcing fiber sheet having a areaweight of 72.0 g/m² was obtained. The two surfaces of this reinforcingfiber sheet were interposed between films made of a polyamide resin(nylon 6, manufactured by Ube Industries, Ltd., product name: 1013B) andhaving a area weight of 45.6 g/m², the fiber sheet was impregnated withthe thermoplastic resin using calendar rolls. Thus, a prepreg having afiber volume percentage content (Vf) of 33% and a thickness of 0.12 mmwas obtained. This prepreg was subjected to incision processing suchthat the reinforcing fibers had a constant length L of 25.0 mm and anaverage cutting length l of 42.4 mm, and the angle θ formed by a slitthat cut the fibers and a reinforcing fiber when viewed in a planar viewwas 45°. A laminated substrate and a molded product thereof wereproduced in the same manner as in Example 1 using a polyester nonwovenfabric, except that the set temperature of the IR heater was adjusted to320° C., the heating time was set to 10 minutes, and the set temperatureof the rib-attached hat channel mold was set to 120° C. Thus, thestamping moldability was evaluated.

As a result, a molded product which had satisfactory surface gloss andwas filled with the laminated substrate up to the tip of the rib, wasobtained.

Example 4

A laminated substrate was produced in the same manner as in Example 2using a glass nonwoven fabric and using the prepreg substrate obtainedin the same manner as in Example 3, and the laminated substrate washeated and pressed under the conditions similar to those of Example 3.Thereby, stamping moldability was evaluated. As a result, a moldedproduct which had satisfactory surface gloss and was filled with thelaminated substrate up to the tip of the rib was obtained.

Example 5

A laminated substrate was produced in the same manner as in Example 3,except that a nylon foamed sheet (manufactured by Inoac Corp.; tradename: ZOTEK NB-50; porosity: 95%) was used instead of the polyesternonwoven fabric, and stamping moldability was evaluated under theconditions similar to those of Example 3. As a result, a molded productfilled with the laminated substrate up to the tip of the rib wasobtained.

Example 6

A laminated substrate was produced in the same manner as in Example 4using a glass nonwoven fabric. Then, stamping moldability was evaluatedin the same manner as in Example 4, except that the glass nonwovenfabric was disposed on both sides of the prepreg substrate, and thelaminated substrate was subjected to stamping molding after heating withan IR heater. As a result, a molded product filled with the laminatedsubstrate up to the tip of the rib was obtained.

Comparative Example 4

A prepreg substrate was produced in the same manner as in Example 3, anda molded product was obtained by heating the prepreg substrate with anIR heater but performing stamping molding without using a nonwovenfabric. Stamping moldability was evaluated. As a result, the surfacegloss was satisfactory, but filling of the rib was insufficientlyachieved.

Example 7

The prepreg obtained in Example 1 was cut into a chip shape whichmeasured 25 mm in the fiber direction and 15 mm in a directionperpendicular to the fiber direction, using a cutting plotter(manufactured by Laserck Corp., product name: L-2500), and thus choppedprepregs were obtained. 220 g of the chopped prepregs were freelydropped from a height of 1500 mm, and thereby the chopped prepregs weredeposited inside a mold cavity which measured 300 mm on each side and1.5 mm in depth. Subsequently, the mold was maintained, using acompression molding machine (manufactured by Shinto Metal IndustriesCorp., product name: SFA-50HH0), for 7 minutes under the conditions of220° C. and an oil pressure indication of 0 MPa with a high temperatureside press. Subsequently, the mold was maintained for 7 minutes underthe conditions of an oil pressure indication of 2 MPa (pressingpressure: 0.55 MPa) at the same temperature, and then the mold wastransferred to a cooling press and maintained for 3 minutes at 30° C.and an oil pressure indication of 5 MPa (pressing pressure: 1.38 MPa).Thereby, an integrated prepreg substrate was obtained. Using thisprepreg substrate, a laminated substrate was produced in the same manneras in Example 2 using a glass nonwoven fabric, and the laminatedsubstrate was subjected to heating and stamping molding Thus, a moldedproduct was obtained, and stamping moldability thereof was evaluated.The molded product obtained as such had satisfactory surface gloss andwas filled with the laminated substrate up to the tip of the rib.

Example 8

Carbon fibers (manufactured by Mitsubishi Rayon Co., Ltd., product name:PYROFILL (registered trademark) TR-50S15L) were cut to a fiber length of6 mm using a roller cutter. Furthermore, an modified polypropylene resinfilm (manufactured by Mitsubishi Chemical Corp., product name: MODIC(registered trademark) P958) was processed into a non-continuous fibrousform having a fiber length of 3 mm. 356 g of these carbon fiber bundlesand 724 g of the resin fiber bundles were introduced into 100 L ofwater, and the mixture was stirred for 10 seconds with a stirrer. Waterwas removed, the solids were dried, and thus a mat-like material havinga area weight of 2,000 g/m² was obtained. 220 g of this mat-likematerial was inserted into a mold cavity which measured 300 mm on eachside and 1.5 mm in depth. Subsequently, the mold was maintained, using acompression molding machine (manufactured by Shinto Metal IndustriesCorp., product name: SFA-50HH0), for 7 minutes under the conditions of220° C. and an oil pressure indication of 0 MPa with a high temperatureside press. Subsequently, the mold was maintained for 7 minutes underthe conditions of an oil pressure indication of 2 MPa (pressingpressure: 0.55 MPa) at the same temperature, and then the mold wastransferred to a cooling press and maintained for 3 minutes at 30° C.and an oil pressure indication of 5 MPa (pressing pressure: 1.38 MPa).Thereby, an integrated prepreg substrate was obtained. Using thisprepreg substrate obtained as such, a laminated substrate was producedin the same manner as in Example 2 using a glass nonwoven fabric. Thelaminated substrate thus obtained was subjected to heating and stampingmolding, and thus a molded product was obtained. The molded productobtained as such had satisfactory surface gloss and was filled with thelaminated substrate up to the tip of the rib.

In the Table, the abbreviation “PP” means polypropylene, and theabbreviation “PA6” means a polyamide resin.

In regard to the evaluation items for surface gloss, a molded productwhich had a smooth surface with gloss was rated as “◯”; and a moldedproduct which had a rough surface and did not show gloss was rated as“X”. In regard to the evaluation items for rib filling, a molded productwhich was filled up to the tip was rated as “◯”; and a molded productwhich was not filled to the tip was rated as “X”.

The evaluation results are indicated in Table 1 together.

TABLE 1 Thermoplastic Heat-insulating Surface Rib resin layer Porositygloss filling Moldability Example 1 Modified PP Polyester 90% ∘ ∘ ∘nonwoven fabric Example 2 Modified PP Glass nonwoven 95% ∘ ∘ ∘ fabricComparative Modified PP None — ∘ x x Example 1 Comparative Modified PPLow-foamed PP 30% ∘ x x Example 2 Comparative Modified PP None — x x xExample 3 Example 3 PA6 Polyester 90% ∘ ∘ ∘ nonwoven fabric Example 4PA6 Glass nonwoven 95% ∘ ∘ ∘ fabric Example 5 PA6 Foamed PA6 95% ∘ ∘ ∘Example 6 PA6 Glass nonwoven 95% ∘ ∘ ∘ fabric Comparative PA6 None — ∘ xx Example 4 Example 7 Modified PP Glass nonwoven 95% ∘ ∘ ∘ fabricExample 8 Modified PP Glass nonwoven 95% ∘ ∘ ∘ fabric

<Discussion>

From the above results, it was found that according to the invention, alaminated substrate having excellent shapeability into a complicatedshape and having excellent moldability particularly at a low moldtemperature, can be provided. It was found that due to the low moldtemperature, warpage caused by post-molding shrinkage is reduced, and amolded product having satisfactory surface characteristics is obtained.Also, it was found that since the laminated substrate has high porosity,gas retention at the time of stamping molding can be suppressed; thathandling during transferring from a heating process to stamping moldingcan be easily achieved by adding functions to the sheet-like material;and that the adhesive strength upon adhesion is increased by using asheet-like material having excellent adhesiveness.

INDUSTRIAL APPLICABILITY

According to the invention, a laminated substrate which has excellentshapeability into a complicated shape and is moldable particularly at alow mold temperature, and a method for manufacturing the laminatedsubstrate, can be obtained.

EXPLANATIONS OF LETTERS OR NUMERALS

-   -   1: Sheet-like material having porosity of from 50% to 99%    -   2: Prepreg substrate including reinforcing fibers and        thermoplastic resin    -   3: Rib part    -   4: Top panel (laminated substrate-charged part)    -   5: Flange part    -   6: Incision    -   7: Reinforcing fiber    -   8: Angle formed by incision and reinforcing fiber    -   9: Cutting length    -   10: Length of cut reinforcing fiber

1. A laminated substrate, comprising a sheet-like material having aporosity of from 50% to 99% laminated on at least one surface of aprepreg substrate including reinforcing fibers and a thermoplasticresin.
 2. The laminated substrate according to claim 1, wherein theprepreg substrate is a prepreg laminated substrate in which pluralsheets of a prepreg including the reinforcing fibers that areunidirectionally oriented and the thermoplastic resin, are laminated. 3.The laminated substrate according to claim 1, wherein the prepregsubstrate is a prepreg substrate in which fiber bundles of thereinforcing fibers or single fibers of the reinforcing fibers aredispersed in the thermoplastic resin.
 4. The laminated substrateaccording to claim 1, wherein the prepreg substrate is a prepregsubstrate in which rectangular chips of a prepreg including thereinforcing fibers that are unidirectionally oriented, are dispersed ina random fashion.
 5. The laminated substrate according to claim 1,wherein the length of the reinforcing fibers that constitute the prepregsubstrate is 10 mm to 100 mm.
 6. The laminated substrate according toclaim 1, wherein the sheet-like material is a sheet formed from athermoplastic resin.
 7. The laminated substrate according to claim 1,wherein the sheet-like material is a sheet formed from inorganic fibers.8. The laminated substrate according to claim 1, wherein the sheet-likematerial is a nonwoven fabric.
 9. The laminated substrate according toclaim 1, wherein the sheet-like material is a foamed sheet.
 10. Thelaminated substrate according to claim 1, wherein the thickness of thesheet-like material is from 0.01 mm to 10 mm.
 11. The laminatedsubstrate according to claim 1, wherein at least one surface of theprepreg laminated substrate is covered by the sheet-like material at aproportion of 30% by area or more relative to the total area of the atleast one surface of the prepreg laminated substrate.
 12. The laminatedsubstrate according to claim 1, wherein the prepreg substrate and thesheet-like material are not adhered.
 13. The laminated substrateaccording to claim 1, wherein the laminated substrate is a laminatedsubstrate for stamping molding.
 14. A method for manufacturing a moldedproduct of a laminated substrate, the method comprising: (1) heating aprepreg substrate including reinforcing fibers and a thermoplastic resinto a temperature higher than or equal to the melting point or the glasstransition point of the thermoplastic resin that constitutes theprepreg, and then laminating a sheet-like material having a porosity offrom 50% to 99% on at least one surface of the prepreg substrate tothereby obtain a laminated substrate, or (2) laminating a sheet-likematerial having a porosity of from 50% to 99% on a prepreg substrateincluding reinforcing fibers and a thermoplastic resin on at least onesurface of the prepreg substrate, and then heating the laminate thusobtained to a temperature higher than or equal to the melting point orthe glass transition point of the thermoplastic resin that constitutesthe prepreg to thereby obtain a laminated substrate, the methodsubsequently comprising introducing the laminated substrate into a moldthat is set to a temperature lower than or equal to the melting point orthe glass transition point of the thermoplastic resin that constitutesthe prepreg, and then stamping molding the laminated substrate.
 15. Themanufacturing method according to claim 14, wherein the temperature ofthe mold is 50° C. to 200° C.